Complex Faulting and Triggered Rupture During the 2018 MW 7.9 Offshore Kodiak, Alaska, Earthquake

Abstract

We combine aftershock relocations, source mechanisms, teleseismic P wave backprojection, and Global Positioning System data inversion to constrain complex faulting geometry of the 2018 MW 7.9 offshore Kodiak earthquake. Relocated aftershocks delineate several N-S trends including a prominent 110-km-long segment, as well as broad NE-SW trends. Global Positioning System modeling and backprojection indicate that the NE-SW trending left-lateral strike-slip segments released most energy dominating far-field crustal deformation and radiated wavefield. Backprojection infers fast E-to-W rupture propagations superimposed on a slower S-to-N migration. We propose a five-segment model of the rupture that was partially driven by dynamic triggering.